- Factor out token constants to kubeadmconstants.
- Move cmd/kubeadm/app/util/{,token/}tokens.go
- Use the token-id, token-secret, etc constants provided by the bootstrapapi package
- Move cmd/kubeadm/app/master/tokens.go to cmd/kubeadm/app/phases/token/csv.go
This refactor basically makes it possible to hook up kubeadm to the BootstrapSigner controller later on